I recently replaced my stock 305 with a 355. I have put about 500 miles on it so far and the trans started acting weird. I takes off fine in first gear but it shifts way late when you are accelerating slow. There is also a slipping feeling in 2nd, 3rd, and O.D. Its like there is nothing there until about 2,500 rpms.........WTF? I checked the fluid and it smells a little burnt. I did just replace the fluid after the engine rebuild. Any ideas anyone?

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1987 Trans Am 355
headers,airfoil,rpm cam, modified MAF and airbox

 

Do you have a THM200-4R? It's a weak transmission and I'd say that your 355 has overstressed it. If the fluid smells burnt and is not clear red and it's shifting like you say, it's toast. The TH-200 ,by design, runs very hot. GM had this idiotic idea that it's better to sacrifice durability for short term fuel economy.

After you have the tranny rebuilt with GOOD STUFF, include a BIG ATF oil cooler!

 

If you don't have the original induction parts then your TV linkage will be out of sync regardless of how you adjust it. A carb for a 350 trans, for example, will not have the proper geometry for a 700. Along with this, if the tranny was marginal it could be toast by now.

 

I still use the TPI for the 355 so all the linkage is the same. Isnt my trans a 700r4? The fluid is still bright red since it isnt very old. I already tried to reset the tv cable. I was thinking maybe the bands or clutches. What do you think?

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1987 Trans Am 355
headers,airfoil,rpm cam, modified MAF and airbox

 

Try readjusting the cable one more time. To adjust the TV Cable skip the book method and do this: Press the D button on the adjuster and loosen the cable setting. Now, have someone floor the gas pedal while you check to see if the throttle plate is open all the way. Usually they are off a little and will wiggle. Do whatever you have to do to get it open solid. Now, with the pedal floored, press the D button and pull the cable back as hard as you can and release the button. You now have the engine, tranny and gas pedal all in sync at WOT. Mark the cable so if for some reason it gets moved you can know where to put it again. The problem with the 'self adjust method' is that it bends things and puts them permanently out of whack. It is also the full TV setting, which is theoretically what the GM method does.

If you still have the same problem then it is likely an internal problem. The 2nd and 4th gears use the same band so if that is burned it affects two gears. The 3-4 clutches are a weak point in this unit and could also be slipping.

If it HOLDS once in a gear then the friction elements should still be usable. If so I would recomend a TransGo Reprogramming Kit (High Performance Shift Kit is another name they call it). If it does hold then this kit will really wake it up. If it slips then it is too late.


[This message has been edited by transfixleo (edited May 16, 2001).]